Subterranean cross country pipelines designed to carry such fluids as water, gas and oil, for example, today are commonly installed at a predetermined level beneath the surface of the ground in trenches, which are back filled after the pipe sections are secured in end-to-end continuity. Such pipe sections often are made from fairly brittle material coated with a corrosion-resistant substance. To preserve the integrity of the pipeline and prevent rupture of the coating, relative fine soil particles frequently are introduced into the trench to serve as a protective padding around the pipeline before the backfilling takes place with heavier material.
The subsoil removed during the trenching operation normally contains large and heavy stones and rocks and some large chunks of clay and earth, as well as earth of a reasonably fine consistency which itself can be utilized as the padding material
While a number of padding machines and methods have been proposed, such as those disclosed in U.S. Pat. Nos. 2,947,096; 3,701,422; 4,057,917; and 4,377,365, none appears to have been sufficiently practical to find widespread adoption. Such a vehicle, to be effective commercially, must be capable of separating the fine earth, or suitable padding material, from the excavated subsoil and delivering it to the trench as the vehicle moves along the trench, and yet the components of the machine must be adjustable so that it can be moved along a highway from job location to job location.